This invention is directed to a family of relayed image-forming optical systems consisting of three conic mirrors. The mirrors are configured so that the system is used off-axis in both aperture and field angle.
The prior art includes Korsch U.S. Pat. No. 4,101,195 which discloses an anastigmat three mirror telescope wherein the primary and tertiary mirrors are ellipsoidal and the secondary mirror is hyperboloid. A fold mirror is positioned at an angle of 45.degree. with respect to the image formed by the primary-secondary mirrors. Offner U.S. Pat. No. 3,674,334 discloses a catoptric anastigmat afocal optical system where the primary and tertiary mirrors are parabolic and the secondary mirror is hyperboloic, see FIG. 3. Additionally, Meinel et al U.S. Pat. No. 4,131,485 discloses in FIG. 2 a solar energy collector and concentrator system having primary and tertiary reflectors, and a secondary of hyperboidal shape.
Additional, more general prior art is represent by the following publications:
(1) Conic Mirrors by H. P. Brueggemann (1968, Focal Press). PA1 (2) Space Optics, Proceedings of the 9th International Congress of the International Commission for Optics, National Academy of Sciences, 1974. PA1 (3) Handbook of Military Infrared Technology, Office of Naval Research, 1965.